Method of coating wire



Juiy 2 39413. M. 5. WHITFIELD fi METHOD OF COATING WIRE Filed Dec. 11, 1939 Patented July 27, 1943 METHOD OF COATING WIRE Marshall G. Whitfield, Louisville, Ky., assignor to Reynolds Metals Company, New York, N. Y.,

a corporation of Delaware Application December 11, 1939, Serial No. 308,693

' 8' Claims. (01. 117414) t This invention relates to the coating of wire, and more particularly to the coating of a metal wire with metals of the general character represented by aluminum. While applicable to the coating of wires of other metals with other coating metals, the invention has been found of particular utility aluminum.

In the coating of ferric wire with aluminum or the like as heretofore practiced, the aluminum coat is likely to have succeeding portions along its length which are of different thicknesses, and this is particularly true if a relatively thick coating of aluminum is desired. Inasmuch as the utility of the coating is ordinarily limited by its least thickness, the regions of increased thickness merely add to the weight and cost without any corresponding increase in benefit-while the irregular cross section resulting is itself a disadvantage. I

The cause for these variations inthickness is not precisely known, but without wishing to be limited .to the correctness of the following theory, it is now believed that these variations in thickness-are attributable to the presence of a relatively tenacious oxide filmat the'surface of the molten bath. Such film is apparently drawn onto the emerging wire along with the coating metal, and tends to adhere to the latter as it congeals on the wire. While the tenacity and elasticity of such surface film permits temporary adhesion to the coating, the resistance to the drag of this film across the molten metal, together with its weight as it tends to follow the wire outof thebath, causes a more or lessperiodic rupture of the fihn. Thus not onlyare portions of the film left on the emerging coated wire, to vary itswith respect to the surface of the bath where it is emerging therefrom, through an orbital path that may take a variety of forms but for convenience is preferably made a closed circular path.

in the coating of ferric wire with 1 It is therefore an object of the present invention to provide a method for coatingwire whereby'a substantiall uniform coating of controlled thickness may be obtained.

Another object of this'invention is'to provide a method of the type characterized whereby a coating of materially greater thickness maybe obtained than has heretofore been the case.

Another object of this iny'entionis to provide a method of the type characterized which is particularly applicable to the coating of ferric wire with aluminum and which enables a substantially uniform and predetermined coating to be formed on the wire that may be several times the thickness heretofore obtainable.

Other object will appear as the description of tus that may be used for effecting the desired movement of the emerging wire.

In accordance with the present invention the wire, where it emerges from the bath, is made to move rapidly, and transversel to the surface of I the bath, through a predetermined orbital path which/within the broader aspects of the present invention, may take a variety of forms as will be apparent to those skilled in the art from the presentdi sclosure,but for convenience of operation and simplicity'of apparatus required it is desirably a path that is circular in form;

Referring to the apparatus illustrated in the drawing, H] designates any suitable container for the bath of molten coating metal, heated in any suitable way to maintain the same properly fluid. The wire II to be coated is introduced into said bath ill in any suitable way, as by means of a nozzle 12 which opens bene'aththe surface of the bath. From the nozzle l2 the wire it passe around any suitable roller i3 mounted in.

any suitable way as by meanscf a bracket It. From the roller t3 the wire it emerges from'the bath, preferably at right anglesto the surface thereof, and as hereshown the wire then passes through a cooling pipe 55 of any suitable length,

form and character (and constitutingno part of the present invention) Then the wire passes through a constraining ring l6, preferably mounted in a ball bearing l1 supported in any suitable way as by an annular frame l8. As here illustrated the ball bearing I1 is retained in the frame l8 by a hinged ring I! pivoted to the frame I8 at and provided with a pivoted locking bolt 2| and nut 22 for cooperation with a slot 23 in said frame I8. Thereby, after backing off the nut 22, the bolt 21 may be pivoted around its axis 24 to release the locking member l9, whereupon the latter may be swung about its pivot 20 to gain access to the bearing I! for inspection or renewal.

From the constraining ring IS the wire passes upwardly through means for moving the wire through its designed path. Where, as here, said path is circular in form said mechanism may take the form of a pulley 25 suitably mounted in a frame 26 as by having its hub 21 which. cooperates with bearing member 28 retained against displacement from said bearing by means of a locking ring 29 suitably secured to said hub as by screw 30. Eccentrically mounted in the pulley 25 is a member surrounding wire H for impressing on the' wire. its'circular movement. As here shown an annular plug 3!, preferably made of a relatively soft metal, such as aluminum, so as not to scratch the surface of the coating, is suitably mounted onthe pulley, preferably for ready attachment and detachment, as

by means of the ball bearing 32 in an annular block 33 secured in the pulley 25. The unit composed of the plug,3l and its bearing 32 may be conveniently attached to the block 33 by a plurality of screws 35, and said block 33 may be secured in the recess 34 by a plurality of screws 35. Pulley 25 is driven in any suitable way from a motor 'or other source of power not shown.

From the plug 3| the wire passes upwardly over a roller 31 and thence to any suitable drum or wire take up machine.

Pulley 25 is preferably rotated at a speed on the order of 1200 R. P. M. While considerable variation in the speed of rotation of pulley 25 may be made, experience has seemed to demonstrate that a rotation on the ,order of 1000 R. P. M. is a critical minimum speed for apparatus of the type illustrated, the effects obtained by the practice of the present invention disappearing, largely if not entirely, if the rotative speed is reduced below this R. P. M.

The rotation of pulley 25 with its plug 3| causes the wire to move through a cylindrical -path whose limits are diagrammatically indicated by the solid and dotted lines of the wire II in the drawing. The upper and lower limits of the movement of the wire are of course determined by the rollers l3 and 31, but other suitable means may be employed if desired. The constraining ring l8 keeps the wire in a nearly cylindrical path and prevents the wire from bellying out toward a loop so as to develop undue stresses therein.

Where the wire H emerges from the free surface 38 of the bath, the wire is rapidly traversing a circular path of small diameter, while the inertia of the molten metal causes it to pile up in the form of a wave at the advancing side of the wire, so that the effect of the movement of the wire through the metal extends an appreciable distance on either side of said path. Hence the rapid traverse of its path by the wire sets up a circular area which by observation may be seento be substantially free of oxide film, the movement of the wire apparently preventing the formation of a film within an area which is slightly larger than that embraced by'the path of the wire. Accordingly the wire emerges through a surface that is substantially free of oxide film, so that the coating is not varied in thickness by portions of film adhering thereto or tending to wipe portions of the coating off the emerging'wire, while the wave piled up in front of the rapidly moving wire apparently assists in effecting a thicker coating.

But whatever may be the physical explanation of the results obtained, experience has demonstrated that for wires of more than 0.10 inch in diameter, whereas the maximum average coating heretofore obtained was approximately 0.64 mil per side, thicknesses averaging from 1.75 mils to 2.0 mils per side may be regularly obtained by the practice of the present invention. With wires less than 0.10 inch in diam-' eter the coatings obtained are somewhat less, but on the same order as compared with earlier accomplishments. The thickness of the coating obtained may be controlled to some. extent by varying the speed of movement of the wire through the emerging surface of the bath.

Therefore, by the practice of the present invention, substantially uniform coatings, which are several times thicker than heretofore obtained, have been regularly secured by the prac-- tice of the present invention in the coating of ferric wire with aluminum. But while the in vention is of particular utility in coating ferric wire with aluminum, it is not limted thereto but has utility where the presence of a film at the surface of the coating bathmay cause irregularities in the thickness of the coating.

While the present invention has been described I in connectionwith an apparatus which causes the wire to traverse a closed path in the form of a circle, it will now be apparent to those skilled in the art that such a path is not of the essence of the invention, although for simplicity of apparatus that character of path has obvious advantages. Byvarying the apparatus used, however, the wire may be caused to pass through closed paths of a variety of other forms, and it is also apparent that other apparatus may be designed for causing the wire to move through a circular path or other form of paths. Various other changes may be made in the details of the procedure without departing from the spirit of this invention, and therefore reference is to be had to the appended claims for a definition of the invention.

What is claimed is:

1. The method of providing a wire with a relatively thick and substantially uniform coating which includes the steps of passing the wire through a bath of molten coating metal and moving said wire transverselyto its length where it emerges from the surface of said bath to cause the wire to rotate along a circular path of small diameter and at a rate in excess of 1000 R. P. M.

2. The method of coating ferric wire with aluminum to provide said wire with a relatively thick and substantially uniform aluminum coating which includes the steps of passing said wire through a bath of molten aluminum and moving said wire transversely to its length where it emerges from the surface of the bath to cause said wire to rotate alonga circular path of small diameter and at a rate in excess of 1000 R. P. M.

3. The method of providing a wire with a relatively thick and substantially uniform co'ating which includes the steps of passing the wire through a bath of molten coating metal, and establishing an uninterrupted wave in engagement with the wire where it emerges from the surface of the bath by continuously moving said wire at a relatively high speed in the same direction through a closed orbital path traced at the surface of the bath.

4. The method of providing a wire with a relatively thick and substantially uniform coating which includes the steps of passing the wire through a bath of molten coating metal and continuously moving the emerging wire cylindrically in the same direction and at a relatively high speed to trace a closed orbital path on the surface of the bath.

5. The method of providing a wire with a rela tively thick and substantially uniform coating which includes the steps of passing the wire through a bath of molten coating metal and continuously moving the emerging wire in the same direction and at a relatively high speed to trace a closed orbital path at the surface of the bath whose dimensions approximate the maximum movement of the wire transversely of its length.

6. The method of coating ferric wire with aluminum to provide said wire with a relatively thick and substantially uniform aluminum coating which includes the steps of passing said wire through a bath of molten alumimun and continuously moving said wire at a relatively high speed around the periphery of a small area at the surface of said bath to generate an uninterrupted Wave in contact with the emerging wire.

'7. The method of coating ferric wire with aluminum to provide said wire with a relatively thick and substantially uniform coating which includes the steps of passing said wire through a bath of molten aluminum and continuously moving said wire at a relatively high speed and in the same direction through a closed orbital path which is substantiallycylindrical in form.

8. The method of coating ferric wire with aluminum to provide said wire with a relatively thick and substantially uniform coating which includes the steps of passing said wire through a bath of molten aluminum and continuously moving said wire at a relatively high speed and in the same direction through a closed orbital path, the magnitude of movement of said wire at the surface of the bath approximating the maximum magnitude of movement of said wire transversely of its length.

MARSHALL G. WHI'IFIEID. 

